Mat forming method and apparatus



Jan. 5, 1960 D. L. SCHUBERT EPA!- MAT FORMING METHOD AND APPARATUS 2 Sheets-Sheet 1 Filed Feb. 7, 1956 'INVENTORS Dale LSchub er-I' BY Harold EEPickson Jan. 5, 1960 D. L. SCHUBERT F-T L 2,919,742

MAT FORMING METHOD AND APPARATUS 2 Sheets-Sheet 2 Filed Feb. 7, 1956 INVENTORS n mm ek 1T wm ffl P n c E a wa a P 0 P i V. B

United States Patent MAT FORMING METHOD AND APPARATUS Dale L. Schubert, Tacoma, and Harold E. Erickson,

Auburn, Wash., said Erickson assignor, by mesne assignments, to Industrial Development Co., Tacoma, Wash, a corporation of Washington Application February 7, 1956, Serial No. 563,878

9 Claims. (Cl. 154--1) This invention pertains to method and apparatus for forming particles into a mat of uniform thickness, which thereafter may be consolidated into a product of uniform thickness and density.

It is common practice in making consolidated products such as hardboard and other pressed fiberboards to reduce wood, cane straw and other lignocellulose to small particles. These are formed dry or moist into a mat on a caul plate made of resilient metal. The caul plate and mat then are transferred into a press, and hot-pressed until the mat has been consolidated to the desired density and thickness.

In these operations control of the thickness of the mat is of primary importance in determining the uniformity of density of the pressed product. If the mat is of non-uniform thickness the pressed product will be of non-uniform density and accordingly may not meet the standards for products of this class.

Control of the mat thickness is difiicult of accomplishment, however, since the metal caul plate upon which it is formed is of substantial size, i.e. in excess of 4 x 8 feet, and becomes warped and distorted as it is alternately heated and cooled during the manufacturing operation. As a consequence, a mat formed upon it by the usual felting procedures will be of uneven thickness, and the pressed product made from the mat of non-uniform density.

It is to the solution of the foregoing problem that the present invention relates, it being the general object of the invention to provide a method and apparatus for forming particles into mats of uniform thickness which there'- after may be pressed into consolidated products of uniform density, using a resilient metal plate which is susceptible to warping and deformation as a supporting surface for the mat during its formation and pressing.

The manner in which the foregoing and other objects of this invention are accomplished will be apparent from the accompanying specification and claims considered together with the drawings, wherein:

Fig. 1 is a view in side elevation of felting, mat leveling and conveying apparatus which may be employed in executing the herein described method;

Fig. 2 is a view-in end elevation, partly in section, of the apparatus of Fig. 1 taken along line 2-2 of that figure;

Fig. 3 is a sectional view taken along line 33 of Fig. 2.and illustrating the construction of the mat leveling means employed in the apparatus of Figs. 1 and 2; and v Fig. 4 is a fragmentary sectional view taken along the line 4-4 of Fig. 3 and further illustrating the construction of the mat leveling means.

Generally stated, the herein described method comprises providing a substantially fiat, resilient plate and forming thereon a mat of particles. The mat is formed in two stages. The first stage includes the forming opera't'ion during which the particles are deposited on the plate. The second includes a leveling operation wherein the mat is scalped or otherwise processed for removing the surface particles and reducing it to a final mat of uniform thickness. Before the leveling operation the plate is flexed temporarily into arcuate form to remove any irregularities caused by warping, corrosion, or handling. A scalping means then is provided which has an arcuate surface conforming to the temporary curvature induced in the plate by flexing it. I

As a further feature of the invention, spacing means may be provided for maintaining substantially constant the distance between the scalping means and the arcuately flexed plate. Such means may comprise for example, retaining means for retaining the longitudinal edges of the plate in a fixed horizontal plane, and a magnetic roller or other pressing means for pressing the central portion of the plate upwardly to a relatively elevated plane. Since the caul plates are made of steel and have magnetic susceptibility, the magnetic roller will engage them closely at all times and as a result the flexed plate will be held securely a fixed and constant distance from the mat scalping means.

- The invention also includes within its scope apparatus for effectuating the above operations.

Considering the foregoing in greater detail and with particular reference to the drawings:

The presently described felting method may be applied to the felting of any of the materials commonly used in the production of hardboard, fiberboard, particle board, and other pressed products. Thus it may be applied to the felting of wood, bagasse, straw, and other annual vegetable products, and also to mineral products.

These various materials may be in the form of fibers, grains, chips, shavings, etc. of any desired size, shape and moisture content. In addition, if they do not have a native binder content which is sufficient for the contemplated purpose, they are mixed with from $6 to ,15 preferably from /2 to 10%, of a suitable binder. Various thermosetting and thermoplastic binders may be used for this purpose, preferred ones being the thermosetting phenol-aldehyde and urea aldehyde resinous condensation products, particularly the thermosetting phenolformaldehyde resins.

In the illustrated embodiment the mixture of particles and native or added binder is introduced by means of a conveyor 10 into a hopper 12. It passes into a felting head 14 wherein are provided suitable means, not illustrated, for transferring its component particles in a dispersed stream to a succession of caul plates 16-22, where they build up into a mat.

As has been indicated above, the caul plates are made of resilient metal and are of substantial size, being sufiiciently large to support a felt measuring as much as 4 x .16 feet. The plates usually are made of steel and accordingly have a magnetic susceptibility. Because of their size, composition and form, they are highly susceptible to deformation induced by handling, corrosion,

and the warping which results from the severe thermal changes to which they are subjected.

Suitable conveying means are provided for conveying the caul plates first beneath the felting head and subsequently beneath a mat leveling means. The conveying means illustrated comprises horizontally spaced apart, endless chains or belts 24, 26. The chains are provided at spaced'intervals with upstanding lugs 28, 30, respectively. A plurality of horizontally spaced apart rollers 32, 34 are provided outside the chains. Accordingly the caul plates may be placed on the chains between the lugs, where they will be supported both by the chains andby the rollers, and will engage lugs 28, 30. Thus I the caul'plates will be driven at a measured and uniform 3 rate when the chains are driven by suitable means, for example by a motor 36.

As the caul plates pass beneath felting head is, there is built up upon them a rough mat or felt 4t! contained between side walls or deckels 42, 44. The surface of this mat is or irregular contour and accordingly the mat next is conveyed beneath suitable mat leveling means. In the described embodiment the leveling means is of the character which scalps or removes material from the surface of the mat to a predetermined depth. Thus the mat leveling means of Fig. 2 comprises a roller 46 having hereon a plurality of longitudinally and radially extending rows of teeth 48. Roller 46 is driven by suitable means, for example, motor 50. As it is driven in a clockwise direction, as viewed in Fig. 1 it scalps the surface of the mat, removing particles therefrom which thereupon are conveyed away by a vacuum conduit 52 communicating with a cyclone separator 54. The latter in turn is connected through conduit 56 to a fan or other source of vacuum 58. The solid material separated in the cyclone then is combined in hopper 12 with the fresh feed from conveyor 10.

For such a leveling means to be effective it is necessary that the caul plates be of regular contour as they pass thereunder. Accordingly the mat leveling means is employed in conjunction with means for flexing each plate, or at least the segment thereof which is immediately below the leveling means. This bends the plate into an arc and temporarily removes any contour irregularities resulting from warping or use, so that an arcuate leveling operation may be performed.

To this end the longitudinal edges of the plate are retained in a fixed horizontal plane by means of side walls 60, 62, which prevent sideways movement of the plate, and rollers 32, 34 and 64, 66, which lock the edges of the plate at the desired elevation. Pressing means then ar provided for pressing the central portion of the plate into a horizontal plane which is diflerent from that at which the edges of the plate are maintained.

Preferably the pressing means comprises a roller 75 mounted for rotation adjacent the central portion of the plate. This roller may be magnetized either permanently or by means of an electromagnet. It need not be a driven roller, since it frictionally engages the surface of the plate and, in the illustrated embodiment, presses it upwardly until the plate assumes an arcuate form which conforms to the generally parabolic curvature of leveling roll 46.

As a consequence, the distance K between the caul plate and the surface of the leveling roll is maintained constant, in spite of the fact that the caul plate may be warped or otherwise deformed. The leveling roll then trims oif the surface of the mat accurately and produces a finished mat 72 of substantially uniform thickness.

After the caul plate carrying the mat has passed beyond the vicinity of the leveling roll, it is permitted to return to its original unflexed condition. As this is done, however, the mat which it carries still retains its uniform thickness. As a result, the caul plate and superimposed mat may be transferred to a press and pressed under suitable conditions to consolidate the mat to the predetermined density and thickness and set the adhesive. In this manner a consolidated product of uniform properties may be obtained.

Having described our invention in preferred embodiments, we claim as new and desire to protect by Letters Patent:

1. The method of forming a mat of particles comprising providing a substantially flat resilient plate, confining the lateral sides of the plate to a fixed plane, flexing the plate laterally into arcuate contour, passing the plate beneath a source of particles, depositing a mat of the particles on the plate, removing particles from the surface of the mat until it is of substantially uniform thickness throughout its arcuate width, and thereafter returning the plate to its normal substantially flat condition.

2. The method of forming a mat of particles comprising providing a substantially flat, resilient plate, confining the lateral sides of the plate to a fixed plane, flexing the plate laterally into arcuate contour, passing the flexed plate beneath a source of particles and in firm sliding contact with laterally spaced fixed deckels, depositing a mat of the particles on the flexed plate between said spaced deckels, removing particles from the surface of the mat while still on the flexed plate until the mat is of substantially uniform thickness throughout its arcuate width, and thereafter returning the plate to its normal unflexed condition.

3. The method of forming a mat of particles which comprises providing a substantially flat, resilient plate, confining the lateral sides of the plate to a fixed plane, flexing the plate laterally into arcuate contour, passing the plate beneath a source of particles, depositing a mat of particles on the plate, passing the mat on the plate beneath mat scalping means for removing particles from the mat surface until it is of substantially uniform thickness throughout its arcuate width, applying a downward pulling force to the under surface of the plate in the area of its longitudinal center for holding the flexed plate a predetermined distance from the mat scalping means while particles are being removed from the mat surface, and thereafter returning the plate to its normal unflexed condition.

4. The method of forming a mat of particles which comprises providing a substantially fiat, resilient plate having magnetic susceptibility, confining the lateral sides of the plate to a fixed plane, flexing the plate laterally into arcuate contour, passing the plate beneath a source of particles, depositing a mat of particles on the plate, passing the mat on the plate beneath mat scalping means for removing particles from the mat surface until it is of substantially uniform thickness throughout its arcuate width, applying a downward pulling magnetic force to the under surface of the plate in the area of its longitudinal cents for holding the flexed plate a determined distance from the mat scalping means while particles are being removed from the mat surface, and thereafter returning the plate to its normal unflexed condition.

5. The method of forming a mat of particles which comprises providin a substantially fiat, resilient plate having magnetic susceptibility, confining the lateral sides of the plate to a fixed plane, passing the plate beneath a source of particles and in firm sliding contact with laterally spaced fixed deckels, depositing a mat of the particles on the plate between said spaced deckels, tempo rarily flexing the plate laterally into upwardly convex form, passing the flexed plate and superimposed mat beneath mat leveling means, maintaining the flexed plate a spaced distance from the mat leveling means by the application of a magnetic force to the under side of the plate in the area of its longitudinal center, and thereafter returning the plate to its normal unflexed condition.

6. Apparatus for forming a mat of particles on a normally substantially flat, resilient plate comprising mat forming means, mat scalping means positioned adjacent the mat forming means, conveying means for conveying the plate successively beneath the mat forming means and the mat scalping means, retaining means arranged to engage the opposite surfaces of the lateral sides of the plate for confining said lateral sides to a fixed plane, and flexing means for temporariiy flexing the plate laterally into arcuate contour during its passage beneath the mat scalping means, the mat scalping means comprising a toothed roll having an arcuate contour conforming to the contour of the laterally flexed plate.

7. Apparatus for forming a mat of particles on a normally flat, resilient plate comprising mat forming means, mat scalping means positioned adjacent the mat forming means, conveying means for conveying the plate successively beneath the mat forming means and the mat scalping means, flexing means for temporarily flexing the 5 plate laterally into arcuate form during its passage beneath References Cited in the file of this patent the mat scalping means and support means for maintaining the transverse dimension of the flexed plate a prede- UNITED STATES PATENTS :gzgggggg mm the mat ScalPing means as it Passes 5 1,101,725 Buchanan June so, 1914 8. The apparatus of claim 7 wherein the resilient plate 1261194 van omum 1918 has magnetic susceptibility and the flexing means com- 115441904 Herb July 1925 prises magnetic roller means for exerting a magnetic force 2,122,473 Hurst et a1 July 5, 1938 on the Plate 2,668,322 Weyerhaeuser Feb. 9, 1954 9. The felting apparatus of claim 7 wherein the reslhent 10 2,693,619 6083 No 9, 1954 plate has magnetic susceptibility and wherein the flexing and support means comprise means for retaining the lon- 2,700,177 P 1955 gitudinal edges of the mat in a fixed horizontal plane, and 2,737,997 Hlmmelheber 6t 81 M 1 19 a magnetic roller positioned centrally of the under side 2,744,848 Mottet May 8, 1956 of the plate for elevating the same above the plane of the 5 longitudinal edges of the plate, the magnetic roller holding FOREIGN PATENTS the central portion of the plate in a fixed elevated position by the exertion of a magnetic force thereon. 1,101,387 France Apr. 20, 1955 

